1. Field of the Invention
The present invention generally relates to centrifugal pellet dryers of the type in which a driven rotor impacts wet pellets exiting an underwater pelletizer against the interior surface of a cylindrical screen which allows water to pass therethrough and the pellets to continue upwardly inside the screen to a discharge outlet. More specifically, the present invention is directed to such a centrifugal pellet dryer in which the housing walls are made of a plastic sheet material to attenuate the noise produced by the centrifugal dryer.
2. Description of the Prior Art
Centrifugal pellet dryers have been effectively used to separate water and moisture from pellets, such as those formed by an underwater pelletizer in which the pellets and water are discharged from the pelletizer cutting chamber as a water and pellet slurry. The water and pellet slurry exiting the pelletizer is typically fed first through a dewatering screen chamber or other suitable water separating equipment to remove the bulk water from the slurry before entering the centrifugal dryer.
Existing centrifugal pellet dryers include an outer housing usually constructed of sheet metal panels, a cylindrical screen oriented in the housing and a driven rotor within the screen for elevating the wet pellets (and entrained water) and impacting the wet pellets against the interior of the screen for separating the water from the pellets so that the water can be discharged through the screen and fall by gravity to a water outlet. The dried pellets are elevated and discharged from an outlet in the area of the upper end of the housing. Existing dewaterers are also constructed with sheet metal panels.
Centrifugal pellet dryers of this general type including a dewatering component are disclosed in the following U.S. patents owned by Gala Industries, Inc. (“Gala”), the assignee of this application: U.S. Pat. Nos. 3,458,045; 4,565,015; 4,896,435; 5,265,347; 5,638,606; 6,138,375 and 6,237,244.
Centrifugal pellet dryers of this type operate on the principle of impact dewatering by utilizing a driven rotor oriented internally of a stationary cylindrical screen with energy being imparted to the wet pellets (and entrained water) by the rotor. The rotor includes peripheral inclined blades to lift the wet pellets (and entrained water) vertically upwardly inside the screen and also to impact the wet pellets (and entrained water) radially against the interior of the screen with moisture being separated from the pellets and discharged through the screen into the interior of the housing.
Centrifugal dryers of this type are quite effective in removing water and moisture from the pellets with the residual heat from the pellets from the pelletization operation further drying the pellets as they are discharged from the upper end of the dryer. Operation of centrifugal pellet dryers of this type, however, produce noise levels that can be objectionable to personnel in the vicinity of the dryers. U.S. Pat. No. 5,265,347 discloses a dryer of this type which is constructed to reduce outward transmission of noise to surrounding areas by constructing the housing with double walls and insulation filling the space between the walls and, preferably, the top and bottom panels of the housing.